LIUI, Dong & Gan & Li, 2021

Dong, Dong, Gan, Zhibin & Li, Xinzheng, 2021, Descriptions of eleven new species of squat lobsters (Crustacea: Anomura) from seamounts around the Yap and Mariana Trenches with notes on DNA barcodes and phylogeny, Zoological Journal of the Linnean Society 192 : -

UROPTYHUS LIUI SP. NOV.

( FIGS 7, 8; SUPPORTING INFORMATION, FIG. S1D)

Zoobank registration: urn:lsid:zoobank.org:act:8D2604C6-10D4-456F-925D-AB70CF8F8B70

Material examined: Holotype, MBM286652 , one ovig. female ( PCL 6.6 mm), stn. FX-DIVE 173, Kocebu Guyot of the Magellan seamounts, West Pacific, 17°23’N, 153°05’E, 1320–1790 m, coll. Faxian ROV on R / V Kexue, 7 April 2018 . Paratypes: MBM286656 , one male ( PCL 4.1 mm), Weijia Guyot , West Pacific, 12°43.85’N, 156°32.38’E, 1703 m, coll. Haima ROV on R / V Haiyang 6, 20 September 2018 . MBM286657 , one male ( PCL 6.7 mm), Weijia Guyot , West Pacific, 12°43.85’N, 156°32.38’E, 1703 m, coll. Haima ROV on R / V Haiyang 6, 20 September 2018 .

Description: Carapace (excluding rostrum) 1.2 times broader than long. Outer orbital angle with tiny acute spine. Lateral margins convex, broadest at posterior branchial margin; anterolateral spine strong, lateral to outer orbital angle and clearly exceeding outer orbital angle; hepatic margins with one or two tiny denticles; branchial margin denticulate (with numerous minute spines), with small but distinct anteriormost spine at lateral end of cervical groove. Posterior margin concave. Dorsal surface with dense fine setae; cervical groove indistinct. Rostrum triangular and elongate, approximately 1.9 times longer than broad, 0.6 times of remaining carapace length and 0.2 times of carapace breadth; distal half slightly upturned; dorsal surface and lateral margins setose; lateral margins each with one to three small spines on distal half. Pterygostomial flap with strong spine on anterior end.

Sternal plastron broader than long, widening posteriorly. Sternite 3 with surface depressed; anterior margin concave, with broad, U-shaped median sinus; anterolateral margin rounded and denticulate. Sternite 4 with pair of short, transverse ridges medially on surface; anterolateral corner distinctly serrated, anteriorly produced, reaching midlength of lateral margin of sternite 3; anterolateral margin straight, 1.6 times of posterolateral margin length. Sternites 5–7 with transverse ridges interrupted by midline groove.

Abdominal tergites unarmed, setose as on carapace.

Telson approximately 2.1 times broader than long; distal portion 1.8 times of proximal portion length, distal margin bilobate, with shallow, broad median notch.

Eyestalk short, reaching proximal 0.2 of rostrum; lateral margins nearly straight; cornea not dilated, approximately 0.6 times of remaining peduncle length.

Antennal peduncle reaching distal third of rostrum. Article 2 with small and acute distolateral spine. Article 4 and 5 each armed with distinct distoventral spine on mesial side; article 5 approximately 1.7 times of the lenghth of article 4. Antennal scale triangular, approximately 3.4 times longer than broad, slightly broader than article 4 and 5, slightly falling short of distal end of article 5.

Third maxilliped slender. Basis unarmed. Ischium slightly shorter than merus; crista dentata with fine denticles. Merus armed with two to four denticles on distal half of flexor margin and distinct spine on distal margin; extensor margin distally rugose. Carpus short; extensor margin rugose, with distinct distal spine.

P1 subequal, approximately 4.2 times PCL; surfaces of each segment having numerous short rugae bearing dense fine setae. Ischium with stout dorsodistal spine; ventral margin produced, with strong mesial subterminal spine. Merus subcylindrical, 1.1 times PCL, 4.1 times longer than broad; distal margin with three moderate-sized dorsal spines, strong mesial spine and two strong ventral spines (each on mesial and lateral side); ventromesial margin with a row of two to five strong spines; ventral surface with one to three small spines along midline. Carpus subcylindrical, longer than merus, 1.4 times PCL, 5.2 times longer than broad; distal margin with three moderate-sized dorsal spines (median spine strongest), strong mesial spine and two ventral spines (each on mesial and lateral side). Palm as long as carpus, 4.5 times longer than broad. Fingers approximately half of palm length; tips acute, slightly crossing over each other; occlusal margins minutely denticulate, with low triangular tooth on base of dactylus, and slightly convex medially on fixed finger.

P2–4 sparsely setose. Ischia short, with small spines on extensor margin. Meri laterally compressed, subequal in breadth and decreasing in length from P2 to P4; P2 merus 0.8 times PCL and 5.3 times longer than broad, P3 merus 0.9 times P2 merus length, P4 merus 0.8 times P2 merus length; extensor margin with a row of small spines (usually rudimentary on distal part and on P4), and strong distal spine on P2; flexor margin with distinct distal spine (usually degenerated as acute corner on P4). Carpi elongate, decreasing in length from P2 to P4; P2 carpus 0.6 times P2 merus length, P3 carpus 0.9 times P2 carpus length, P4 carpus 0.8 times P2 carpus length; extensor margin rugose proximally (sometime with minute spines) and with distinct distal spine (somewhat rudimentary on P3 and P4 of the holotype). Propodi subequal in length and breadth from P2 to P4, 0.9 times P2 merus length, and four times as long as broad (measured at distal convex part); flexor margin distally convex, with seven to nine corneous movable spines (including distal pair) evenly spaced on convex part. Dactyli much setose, approximately half of propodi length, distinctly curved and gradually narrowing distally, terminating in strong claw; flexor margin with seven movable corneous spines evenly arranged on entire length, spines decreasing in size proximally.

Coloration: Carapace, abdominal segments and pereopods generally light orange; gastric region, rostrum and midline of abdominal segments deep reddish-orange.

Habitat: Associated with an unknown black coral.

Distribution: South China Sea and Magellan Seamounts, West Pacific; 1200–1790 m.

Etymology: The specific name commemorates Professor Liu Ruiyu, current leader in Crustacean biology in China.

Remarks: The paratypes from Weijia Guyot are more spinose on the pereopods: the P1 merus has several small spines along the mesial margin; the P1 carpus has one to four small spines or pointed tubercles on dorsomesial margins (more pronounced proximally); the spines on the extensor margins of the P2–4 carpi are much more pronounced.

The new species is morphologically similar to U. hamatus Khodkina in Zarenkov & Khodina, 1981 and U. subsolanus Ahyong & Poore, 2004 from the western or south-western Pacific in the following characters: the branchial margins have denticles and spines; the rostrum has lateral spines distally; the dorsal surface of the carapace has no epigastric spines; anterolateral spines are slender reaching level of cornea; and possess the same shape and spine arrangement on the P2–4 propodi and dactyli. The new species can be distinguished from U. hamatus in having dorsal surface of P1 merus and carpus unarmed instead of armed with a row of spines, anterior margin of the sternite 3 with U-shaped median sinus instead of without median sinus or notch, and the anterolateral corners of the sternite 3 rounded instead of terminating in strong spines. The new species is different from U. subsolanus in having P2–4 meri armed with spines instead of unarmed on extensor margin, antennal scale falling short of instead of distinctly over-reaching distal end of the antennal peduncle, pterygostomial flap unarmed instead of with small spines on lateral surface, and the anterolateral corners of the sternite 3 rounded instead of armed with acute spines. Uroptychus liui also resembles U. ritchie Schnabel, 2020 in having small spines on branchial lateral margins and similar spination patterns on P1. The new species can be distinguished from U. ritchie in having the dorsal surface of carapace totally unarmed and the flexor margin of P2–4 propodi distally convex; whereas U. ritchie has a row of small and obsolescent spines across epigastric region, and the flexor margins of P2–4 propodi entirely straight ( Schnabel, 2020).

Uroptychus liui is genetically close to U. insignis ( Henderson, 1885) , U. macquariae Schnabel, Burghardt & Ahyong, 2017 and U. spinulosus Dong & Li, 2015 (see below). The new species differs from these species in having the carapace unarmed instead of with a row of epigastric spines on the dorsal surface. In addition, U. insignis and U. macquariae have branchial margins much more spinose instead of denticulate (except the anteriormost spine) in the new species. Uroptychus spinulosus has smooth hepatic margins and P2–4 propodi with additional corneous spine distinctly proximal to the distal projection, whereas the new species has denticulate hepatic margins, and P2–4 propodi unarmed except for spines on the distal projection.

No DNA barcode information for U. hamatus or U. subsolanus is available for comparative study. The COI genetic distances between the holotype and paratypes from the Weijia Guyot are 0.0–0.2%. The COI genetic distances between the new species and U. insignis and U. macquariae are 3.5–3.7% and 6.6–7.0%, respectively ( Schnabel et al., 2017), showing distinct genetic divergences among these species. Therefore, considering the distinct morphological and genetic differences, U. liui can be treated as a separate species from U. insignis and U. macquariae . We failed to obtain COI and 16S sequences from the small holotype of U. spinulosus , but a 240-bp fragment of the H3 gene was obtained. H3 is a relatively conserved gene and, therefore, usually has a lower genetic distance than COI and 16S (e.g. Rodríguez-Flores et al., 2019a). The genetic distance between the holotype of the new species and U. spinulosus based on the H3 sequence is 3.0%, indicating a significant genetic difference.